Gorin



,Aug. 2,1,195s' EGORIN '2,759,915

HYDROCARBON SEPARATION Original Filed Sept. l5, 1949 2 Sheets-Sheet 1 /4/ 55m/24pm 7 WASH/N@ 25 Ey- Z Evra/F065 /24 INVEN TOR.

12x/Bm @lg/m9 Aug. 21, 1956 Original Filed Sept, l5. 1949 E. GORIN HYDROCARBON SEPARATION 2 Sheets-Sheet 2 we@ 25M United States Patent O HYDROCARBON SEPARATION Everett Gorin, Pittsburgh, Pa., assignor to Socony Mobil Oil Company, Ine., a corporation of New York Original application September 13, 1949, Serial No. 115,518, now Patent No. 2,642,423, dated June 16, 1953. Divided and this application January 15, 1952, Serial No. 266,547

3 Claims. (Cl. 260--96.5)

This invention has to do with the separation of hydrocarbons and hydrocarbon derivatives of different molecular configuration from mixtures containing the same, and also has to do with the preparation of new and novel compositions.

This application is a division of application Serial No. 115,518, filed September 13, 1949, Patent No. 2,642,423, which, in turn, is a continuation-in-part of application Serial No. 4,997, filed January 29, 1948, now abandoned.

I. FIELD OF INVENTION Numerous processes have been developed for the separation of hydrocarbons and `hydrocarbon derivatives of different molecular conguration by taking advantage of their selective solubility in selected reagents or solvents from which they may later be separated. Exemplary of hydrocarbon separation procedures is the Edeleanu process, wherein paraiinic materials are separated from aromatics by virtue of the greater solubility of aromatics in liquid sulfur dioxide. Lubricant oil solvent refining processes, solvent deasphalting, solvent dewaxing and the like are further examples of the separation of hydrocarbons of different molecular configuration. Typical of selective solvent procedures for separa-ting hydrocarbon derivatives is the separation of parafn wax, monochlorwax and polychlor waxes, with acetone as the selective solvent.

This invention is concerned with the general eld Outlined above, but based upon a diiferent and little-known phenomenon, namely, the differing ability of hydrocarbons and hydrocarbon derivatives to enter into and to be removed from certain crystalline complexes. As used herein, the -term complex broadly denotes a combination of two or more compounds.

This invention is predicated upon the knowledgev that urea forms complex crystalline compounds to a varying degree with various forms of hydrocarbons and hydrocarbon derivatives.

II. PRIOR ART For some years it has been known that various isomers of aromatic hydrocarbon derivatives form complexes with urea. Kremann (Monatshefte f. Chemie 28, 1125 (1907)) observed that complexes, designated -as double compounds, of urea and the isomeric cresols are stable at different temperatures. Schotte and Priewe (1,830,859) later separated meta-cresol from the corresponding para isomer by selectively forming a metacresol-urea complex, which was described as an addition compound; the latter compound was separated from the para isomer and then split up by distillation or with Water or acid to obtain pure meta-cresol. The addition compound of rneta-cresol and urea was shown thereafter to have utility as a disinfectant (Priewe- 1,933,757). Bentley and Catlow (1,980,901) found a number of aromatic amines containing at least one basic amino group capable of forming double compounds with certain isomeric phenols. It has also been shown that trans-oestradiol can be separated from the corresponding cis-compound by forming a diicultly soluble Patented Aug. 21, e

2 compound of urea and trans-oestradiol (Priewe- 2,300,134).

The forces between urea and the compounds of the foregoing complexes are due to specific chemical interaction between the various functional groups.

One heterocyclic compound, 2:6 lutidine, has been found to form a crystalline compound with urea, thus affording a means of separating the lutidine from betaand gamma-picolines (Riethof-2,295,606).

Comparatively few aliphatic hydrocarbon derivatives have been known to date to form complex compounds with urea. In German patent application B 190,197 IV d/ 12 (Technical Oil Mission, Reel 143; Library of Congress, May 22, 1946) Bengen described a method for the separation of aliphatic oxygen-containing compounds (acids, alcohols, aldehydes, esters and ketones) and of straight chain hydrocarbons of at least six carbon atoms from mixture containing the same, the method being predicated upon the ability of such compounds and hydrocarbons to form Additions-Produkt with urea. In the Technical Oil Mission translation of the Bengen application, however, the urea complexes were designated adducts, which term apparently stems from the anglicized addition product.

III. DEFINITIONS From the foregoing discussion of prior art (Il), it will be clear that a variety of terms have been applied to urea complexes. The latter have been rather loosely described as double compounds, addition compounds, dicultly soluble compounds, Additions-Produk and adducts. All of these terms are somewhat ambiguous in that they have also been used to describe produc-ts or complexes of different character than the urea complexes under consideration. This is particularly so with the term adduct, and the related term unadducted material. While the term adduct is simple and convenient, it is an unfortunate designation, inasmuch as it confuses these complexes with other substances known in the chemical art. Specifically, adduct has been applied to Diels-Alder reaction products, formed by reaction of conjugated diolens and oleiins and their derivatives. As is well known, Diels-Alder products, as a rule do not revert to their original constituents when heated or treated with water, acids, solvents, etc. Moreover, the term adduct has been defined earlier as The product of a reaction between molecules, which occurs in such a way that the original molecules or their residues have their long axes parallel to one another. (Concise Chemical and Technical Dictionary.) Further ambiguity is introduced by the term adduction, which has been dened as oxidation (Hackh.)

To avoid the foregoing conicting terminology, several related terms have been coined to define with greater specificity the substances involved in the phenomenon under consideration. As contemplated herein and as used throughout the specification and appended claims, the following terms identify the phenomenon:

Plexad--a revertable associated complex comprising a plexor, such as urea, and at least one other compound; said plexad characterized by reverting or decomposing, under the influence of heat and/or various solvents, to its original constituents, namely, a plexor and at least one plexand;

Plexand-a compound capable of forming a plexad with a plexor, such as urea; compounds of this character difer in their capacity to form plexads, depending upon various factors described hereinafter;

Antip'lex--a compound incapable of forming a plexad with a plexor;

Plexor-a compound capable of forming a plexad with a plexand; such as urea;

Plexate-to form a plexad;

Plexation-the act, process or eiect of plexating.

IV. STATEMENT OF INVENTION It has now been discovered that, by selective plexation with urea, certain aliphatic hydrocarbons and aliphatic hydrocarbon derivatives of varying degrees of saturation (or unsaturation) can be separated, in the form of their corresponding plexads, from a mixture containing the same. One particular selective plexation involves separation of more saturated straight chain hydrocarbons and hydrocarbon derivatives from less saturated straight chain hydrocarbon and hydrocarbon derivatives, for example, a saturated parain from a mono-olefin, particularly when the olein group is relatively centrally positioned in the molecule; also a mono-olefin from a poly-olen, particularly when the oleiin groups are relatively centrally positioned and are spaced an appreciable distance from each other. Another selective plexation involves separation of a straight chain hydrocarbon, or hydrocarbon derivative, having a double bond at or close to a terminal carbon atom, from a hydrocarbon, or hydrocarbon derivative, having a double bond more centrally positioned in the hydrocarbon chain. The separation procedures are effective when the aliphatic hydrocarbons and aliphatic hydrocarbon derivatives present in the mixtures subject to plexation have the same or a different number of carbon atoms. Selective plexation is also effective when the aliphatic hydrocarbon derivatives have the same or different substituent groups.

As contemplated herein, the invention makes possible the separation of one or more plexands from a mixture containing the same, such plexand or plexands being separated in the form of a plexad or plexads which, as described in detail hereinbelow, revert to the plexor, urea, and the plexand or plexands under certain conditions. The separation, therefore, is an excellent means for obtaining, in pure or concentrated form, one or more plexands or antiplexes whichever is the desired material. The invention also provides a means of forming new compositions of matter, namely, a number of plexads which may be used as a source of a plexor, urea, or as a source of a plexand.

V. OBJECTS It is an object of this invention, therefore, to provide an effective means for separating hydrocarbons and hydrocarbon derivatives of different `degrees of saturation, or unsaturation, from mixtures containing the same.

It is also an object of this invention to selectively separate a straight chain saturated hydrocarbon from a mixture containing the same and a straight chain unsaturated hydrocarbon. A more particular object is the separation of a straight chain paratiin from a straight chain monoolen, especially when the olen group is relatively centrally positioned in the molecule. A related object is the separation of a straight chain saturated parain derivative from a mixture containing the same and a straight chain unsaturated paraffin derivative. A particular object is the separation of a straight chain saturated acid from a straight chain unsaturated acid.

A further object is the provision of a selective separation of a straight chain mono-olen from a mixture containing the same and a straight chain poly-olen. A particular object is the separation of Ia straight chain mono-olefin from a straight chain diolen, especially when the olefin groups are relatively centrally positioned and are spaced an appreciable distance from each other. A related object is the separation of a straight chain monoolefinic parain derivative from a mixture containing the same and a straight chain poly-olefinic para'in derivative. A more particular object is the separation of a straight chain mono-olenic acid from a straight chain polyolefinic acid.

' l-dodecene An additional object is the separation of a straight chain mono-olen having the double bond at a terminal carbon atom, from a mixture containing the same and a straight chain mono-olen having the double bond more centrally positioned in the hydrocarbon chain. A corresponding object is the separation of a straight chain mono-olefin having an internal double bond from a mixture containing the same and a straight chain monoolen having an internal `double bond more centrally positioned in the chain.

Another object is the provision of a continuous method of separation of said plexands and antiplexes, which method is exible, capable of relatively sharp separation, and not highly demanding of attention and of utilities such heat, refrigeration, pumping power, and the like.

Still another object is to provide a plexand or plexands substantially free of an antiplex or antiplexes. A corresponding object is the provision of an antiplex or antiplexes substantially free of said plexand or plexands.

Another object is to provide a new and novel class or sub-classes of plexads comprisingl a plexand and urea.

Other objects and advantages of the invention will bc apparent from the following description.

VI. INVENTION IN DETAIL As indicated above, it has been found that the forcgoing objects are achieved by selective plexation with urea (a plexor) of a plexand or plexands.

(l) Plexalzds A plexand, as dened above, is a compound capable of forming a plexad with a plexor, such as urea. Contemplated herein as plexands are a variety of parainic compounds.

(a) Parains.-Bengen, identified above, has disclosed that straight chain paratlins having at least six carbon atoms per molecule form complexes, or as dened herein plexads, with urea. Such parains, therefore, are corisidered as plexands in the process of this invention.

Typical of such paraflins are the following: n-Oetane n-Nonane n-Heptane n-Decane, etc.

(b) Unsatumted comp01mds.-It has now been found that normal, alpha oleiins having no more than two additional non-terminal double bonds and at least about seven carbon atoms per molecule, are plexands. It has also been found that stronger plexadsy are formed of such normal, alpha olens, than of the corresponding olens having a double bond more centrally positioned in the carbon chain. In other words, the forces between urea and the olen making for plexad formation, become progressively weaker as the double bond migrates towards the center of the molecule. Accordingly, normal, nonalpha oleins are considered herein as secondary plexands, as shown hereinbelow.

In addition, it has' been discovered that the straight chain parati-ins form somewhat stronger plexads with urea than do the straight chain, normal alpha mono-oieins which, in turn, form stronger plexads than the straight chain diolens. Further, under the same conditions, straight chain polyoleins containing three or more double bonds do not form plexads.

Representative normal, alpha olein plexands are the following:

1,3-decadiene 1,4-decadiene 1,17-octadecadiene l-nonadecene 1,9-decadiene l-eicosene l-undecene l, l9-eiscosadiene 1,10-undecadiene l-docosene l-tricosene 1,1 l-dodecadiene l-tetracosene letridecene lnhexacosenetcerotene) The correlation between the width ofI the terminal 1-tetradecene l-heptacoseneiY substituent and the length of the carbon chain required 1,4tetradecadiene l-octacosene for plexad formation at 25 C. is an approximate one.

. This relationship depends to some extent upon the nature (c)Termmally-substztuted parafns.-As described 1n several related applications, Serial Nos. 115,511, now 5 or. the Subsmuent as Well as upon the Wldth of the Sub' abandoned, 115,513, Patent NQ 2,642,422, 115,514 stituent. For example, in the case wheretwo substituents new abandoned 115 515 Patent Nn. 2 681332 115 516 are .)f the .same me the group Whch-1mltfts a higher new abandoned 116,593 Patent No. 2681f334and ,115- meltmg Pom to the subsumed Param W1 form the stronger plexad, i.,e. will form a plexad when the chain is somewhat shorter in length. Caproic acid, melting point -1.5 C., thus preferentially forms a plexad with saturated urea at 25v C., whenV admixed with n-hexyl alcohol, melting point -51.6 C.

517, Patent No. 2,681,333, all iiled September 13, 1949, certain terminally-substituted straight chain parains are plexands. These paranic compounds have been represented by general Formula A:

(A) X(CH2)1VCH3 Only the carbon atoms in the chain are considered to whereinnisawhole number and whereinXisasubstituent Contribute to the chain length, thatlS, aOmS Such aS group of the character described below, with n and X oxygen, sulfur, nitrogen, etc., are not included in the beinginterrelated atom total. Accordingly, then, the straight chain com- The substituent group X can be an inorganic or organic pounds contemplated herein include straight chain aligroup, such as illustrated by the following; pha'tlc llyClIOCalbOIllS` and Straight Chain aliphatic hydro- (a) Halogen substituent: F, C1, BI. and I; carbons in which one or more of the carbon atoms of the (b) Nitrogen-containing substituent: NH2, NH(R), NRZ, chain .have been replaced by such atoms as oxygen, sul-` No2, NoH, CN, CoNHd, CoNH(R), CoNR2, CNO, fur mffogen and the likeh d b It is possible, however, to give the unequivocal limits SaliscalNCO NCS etc Wherem R 1S a y Tocar on for the relation between widthj of the terminal substit- (c) Sulfupcoutaining substituent: SH SR SOBH, OSOaH, uent and size of the carbon chain required for plexation SOZH SO2R SOR wherein R is a hydrocarbon radical with urea at 25 C. These limits are set forth in Table SOzZ wherein Z is a halogen atom, etc.; H below:

Oxygen-Con'tllilgg substituent: OH, TABLE IL CORRELATION BETWEEN uVIDTHn OF TER COOR, wherein R is a hydrocarbon group, CO, O-, MINAL sUBs'IITUEN'I AND MINIMUM CHAIN LENGTH CI I2OI I7 etc.; 30 FOR UREA. PLEXATION AT 25 C.

(e) Cyclic substituent: cycloalkyl such as cyclopropyl,

cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, chlor- Minimum cyclohexyl, etc.; aryl such as phenyl and chlorphenyl; Chain hetero such as nnenyi C4H3s, finyi CiHao, pyrryi Gmup (221% r C4H4N, pyridyl Cal-14N, thiazyl CsHzNS, pyrazolyl 35 Offllgn C3H3N2, piperydyl CsHioN, etc.;

(f) Alkyl substituent: methyl; 2 3 5 8 (g) Alkenyl substituent: vinyl; 2. B-sf 7 8-12 (h) Haloalkyl substituent: dichlormethyl Cl2CH-, etc. 3 lg The substituent group (X) can be any of the types outlined above subject, however, to one important consideration, namely, that of geometrical size as related to the It iS to be understood that these limits apply for PleXanumber 0f Carbcm atoms in the Chain, The Width of tion at temperatures of the order of about 25 C. The

the substituent group is the geometrical feature to be conmlrllmllm Humber 0f CarbOn 2101118 in the Chain is lower sidered, and this is the cross-section of the group taken in for PleXaloIl all loWer temperatures, but generally Ilot a direction perpendicular to the bond joining the group more than one o1' WO Carbon atoms lower; that iS, With to the carbon chain. This distance is taken atthe widest olle leSS Carbon atom the minimum number of Carbon portion of the group and may be conveniently given a atoms is six. In the same Vein, for an increase in temperquantiative measure as the distance from between outer atllre: a correspondingly higher Dumber of Carbon atoms covalent radii of the two most widely separated atoms Will be required in the Challll h, along the cross-section of the group where the covalent By Way of lllUSfalOD, the following compounds repreradii are those given by Pauling (Pauling-Nature of sented by general Formula A are tyPloal PleXerldS The Chemical Bond; Cornell University Press; Ithaca; (a) Halogen ComPolI1d-S1 11-heptyl fluoride, n-heptyl N. Y 1939) The Width determines the length of the bromide, n-octyl chloride, n-octyl bromide, n-dodecyl carbon chain required to obtain plexation at about 25 C. 55 iodide nhexadeyl chloride n'hexadecyl bromide with a saturated urea solution, a plexor. In the case of neoeladeeyl Chl0r 1d e, I10Cadey1 bromide, etc.; composite groups of the type-COY, -CHzCOY and (b) Nltrogen'contammg compounds: -CH2Y, wherein Y is a non-aliphatic radical such asy AmlflO-n'octylamme? I ldecylamme; n'hexadecyla' chlorine or amino, the =C=O, CI-12C() and CH2 mine; n-octadecylamine; methyl, n-octylamine; constitutents, respectively, are considered as part of the butyl n'octylamln; carbon chain and the width computed is that for the Cyaw-n'hexyl mmlez 1 1`Octy1 mde n'tetradecyl radical Y' .nitrile, n -octadecyl nitrileaetc.

The Widths of a number of typical groups computed Nitro--l-nitro-n-decane; 11iitr0ndodecane; l-nitroaccording to the method given above are listed in order noctadecane; etai; of Size in Table I below: 60 Amido-n-octanamidlel, l n-dodecanamide, n-octaden f u u canamide; N-me y noctanamideg N-hexyl, 'IABLL I.- WID FH 0F VARIOUS GRoUPs IN A n decanaml-de; en

L20 M6 Cyanate and isocyanate-n-hexyl cyanate, n-hexyl 1 28 2.67 isocyanate, n-decyl cyanate, n-decyl isocyanate, i. gg n-hexadecyl cyanate, n-hexadecyl isocyanate, etc. 1:98 4138 Thiocyanate and isothiocyanate-n-decyl thiocyanate; n-decyl isothiocyanate; n-octadecyl thiocyan- 2128 2 or gmethyl yclohexyl 514;, ate; n-octadecyl isothiocyanate; etc. 2.36 0-orm-to1y1 6.09 (e) Sulfur-containing compounds:

Mercapto-noctyl mercaptan, n-dodecyl mercap- 7 tan, n-hexadecyl mercaptan, n-octadecyl mercaptan, etc.

Sulfido (SR)-methyl, n-octyl sulfide; n-butyl, n-dodecyl sulfide; amyl, n-heXadecyl sulfide; etc.

Sulfato-n-dodecyl sulfate; n-hexadecyl sulfate; etc.

Sulfonyl halide-n-decyl sulfonyl chloride; n-dodecyl sulfonyl bromide, n-hexadecyl sulfonyl iodide, etc.

Oxygen-containing compounds:

HydroXy-n-heptanol- 1; n-octanoll; n-decanol-l; n-dodecanol-l; n-heXadecanol-l; octadecyl alcohol; etc.

Carboxyl-n-valeric acid; caproic acid; n-heptylic acid; caprylic acid; pelargonic acid; lauric acid; myristic acid; palmitic acid; stearic acid; arachidic acid; behenic acid; lignoceric acid; cerotic acid; etc.

Keto-di(nbutyl) ketone; methyl, n-heptyl ketone;

ethyl, n-heXyl ketone;

Ether-di(nbutyl) ether; ethyl, n-pentyl ether; di-

(n-pentyl) ether; etc.

Ester-di(namy1) succinate; n-butyl stearate; etc.

(e) Cyclic substituent: 1-cyclopropyl-n-octadecane; l-cyclohexyl-n-hexadecane; l-phenyl-n-octadecane; l-thienyl-n-octadecane; etc.

(f) Alkyl substituent: n-octane; 2,2 dimethyln octadecane; etc.

(g) Haloalkyl substituent:

etc.

It is to be understood that terminally-substituted straight chain compounds containing a second terminal substituent on the opposite terminal carbon atom, are also contemplated herein as plexands- Such disubstituted compounds are also subject to approximately the foregoing relationships of terminal group width and chain length. Compounds of this character are represented by the following general Formula A:

(A) X( CH2) X wherein n is a whole number, and X and X' are the same or different and as defined above.

Illustrative of such compounds are the following:

1,10-dichlor-n-decane; 1,8-n-octane diamine; 1,10-n-decane diamide; 1,12-n-dodecane dithiol; l,18-disulfo-n-octadecane; etc.

(d) Terminally-subszituted defina-Straight chain olefinic compounds having a terminal substituent and not more than two non-terminal double bonds, are also considered as plexands herein. The terminal substituents are of the character described above in connection with the related paraftins VI(l)(c). Here too, the same relationship of width of terminal substituent and carbon chain length is an important consideration. The relationship shown above is in operation with the olefinic compounds subject, however, to some influence of the degree of unsaturation. In some cases, the presence of one double bond will require a chain of one or two more carbon atoms than are shown in connection with VH1) (c) By way of illustration, the following terminally-substituted, normal olefins are typical plexands:

1-chloro-n-octene-2; l-amino-n-decene-Z; n-Octadeceneamide;

Oleic acid;

Oleyl alcohol; n-Octadecenyl mercaptan.

Included also as plexands are terminally-substituted, straight chain non-alpha olefins having less than three double bonds per molecule. Here too, the widt of the substituent group and the number of carbon atoms in the chain are interrelated, and the values given above for compounds represented by general Formula A are substantially in operation.

By way of illustration, the following compounds typify terminally-substituted, straight chain non-alpha olefins:

n-9-hexadecenylamine; n-9-octadecenylamine;

n-9, 12-octadecadienylamine; n-9-octadecenylamide;

Oleyl alcohol; DeIta-Q-lO-decenylic acid; Delta-9-l0-dodecenylic acid; Oleic acid;

Ricinoleic acid;

Linoleic acid; Z-ethyIheXyLn-octyl fumarate; Di-(n-hexyl) fumarate; Di-(n-octyl) fumarate; Di-(n-hexyl) maleate; Di-(n-octyl) maleate; n-Butyl oleate; etc.

It should be noted that 2-ethylhexyl, n-octyl fumarate forms a plexad with urea, thus demonstrating that a relatively small degree of branching can be tolerated, that is, one ethyl group in a linear chain containing eighteen carbon atoms. However, di-(Z-ethylhexyl) fumarate does not form a plexad under the same conditions, apparently having too high a degree of branching.

Another feature to be noted is the failure of di-(n-amyl) fumarate to form a plexad with urea at 25 C. This demonstrates the insufficiency of the amyl chains, for `at least one of the chains should contain at least siX carbon atoms. For example, di-(n-hexyl) fumarate forms a plexad under the same conditions. Dioleyl maleate, however, does not form a plexad under these conditions, evidence that the degree of unsaturation, three double bonds, is too high for plexad formation.

It is to be understood that terminally-substituted straight chain olefins containing a second terminal substituent attached to the opposite terminal carbon of the chain, are also contemplated as plexands. These disubstituted olefins are subject, too, to the terminal group width and and chain lengths applicable to the substituted olefins above.

Typical of disubstituted olefins having at least one terminal substituent are the following:

Chloro oleic acid; Ricinoleic acid; etc.

(2) Secondary plexands The compounds described below are secondary plexands in the processes of this invention.

(a) Parafjns.-Parafiins serving as secondary plexands are primarily straight chain in character with but little branching. In general, these parafiins should contain at least about ten carbon atoms in a straight chain, with the branch chain being attached to another carbon atom of the chain and with the branch chain having less than three carbon atoms.

Illustrative of such parafiins is 2-methyl-n-hexadecane.

(b) Olens.-Straight chain, non-alpha oleiins having less than three double bonds and having at least about seven carbon atoms per molecule, form plexads with urea. As indicated above, plexads of such olefins are not as strong as those formed with the alpha olefins defined above. The difference in the forces attending a pleXad of a lolefin and a plexad of a 2-o1efin is, therefore, substantially less than the corresponding difference with a l-olefin and a 4-, 5- or -olen. Applying this relationship, a more effective separation is made of a 1- oleiin from a 4-olefin, than of a l-olefin from a 2-oletin. In the latter instance, however, a considerable upgrading of the l-olefin content is realized, particularly by repeated contact with urea. i

9 Representative non-alpha olens behaving as secondary plexands are the following:

Both the cis and trans form of the olens are contemplated herein; however, the trans compounds will genorally form the stronger plexad.

(c) Non-terminally substituted compounds- Secondary pleXands also include non-terminally substituted, straight chain compounds characterized by general Formula B:

wherein r and m are integers, the sum of which is equal to or dilerent than n-2, and n and X are as defined above.

The length, rather than the width, of the substituent group (X) roughly determines the minimum carbon chain length required for plexation of a secondary plexand. The length is the projection along the bond joining the group to the parent hydrocarbon of the distance from the center of the carbon atom to which the group is attached, to the center of the atom whose covalent radius shell extends furthest in the direction of said bond, plus the covalent radius of said bond. The minimum chain length is also to some extent a function of the position substituted as well as of the chemical nature of the group. Thus, in compounds of this type, the minimum chain length required for plexation is determined by the length of group H3C(CH2)r-, if r is small enough so that this alkyl group is shorter in length than the substituent group (X). It is possible, bearing this relationship in mind however, also to give rather wide limits 1n the correlation of group length with the minimum chain length required for pleXation. The lengths of varlous groups are given in Table III, below, while the correlation of chain lengths with group lengths 1s given 1n Table IV, also provided below:

TABLE III.-"LENGTHS F VARIOUS GROUPS IN 11 2. 06 -SH 2.85 2.10 3.05 2.17 3.11 2.31 3.19 2. 43 3. 25 2. 61 3.37 2.70 3.43 2. 76 h yl (average 5.09 2. 81 -Phenyl 5. 69

TABLE 1v.-ooRRELA'rIoN BETWEEN LENGTrr' 0F NON-TERMINALLY SUBSTITUTED GROUPS AND MINI- plexation at lower temperatures, but generally not more than one or two carbon atoms lower. In the same vein,

a correspondingly higher number of carbon atoms will be required in the carbon chain for a rise in temperature. Secondary plexands represented by general Formula B, above, are typied by the following:

2-,chloro-n-tetracosane;

Z-amino-n-decane;

2-nitro-n-octadecane;

n-Octanol-Z; etc.

(3) Antiplex antiplex, as defined above, is a compound incapable of forming a pleXad with a plexor, such as urea.

Compounds which have been found to have as antiplexes in the sense that they are incapable of forming a plexad with urea at about 25 C., include:

Z-ethylhexene-l n-Butyl amide .Diisobutylene n-Butyric acid Triisobutylene n-Butyl alcohol Dioleyl maleate n-Amyl alcohol n-Butyl bromide n-Hexyl alcohol n-Butylchloride l-'I'hienyl-n-dodecane n-Amyl chloride (4) Plexor The plexor used herein is urea, which is in solution in a singleor multiple-component solvent. This solution should range from partially saturated to supersaturated at the temperature at which it is contacted with a plexand or with a mixture containing one or more plexands and antiplexes, and, in many cases, it will be found convenient to suspend a further supply of urea crystals in the solution, handling it as a slurry. For gravity or centrifugal separation, it is convenient to use a solvent of such a specific gravity that after the formation of a desired amount of plexad, the specific gravity of the solvent phase will be different from that of the plexad phase and of the antipleX -phase to a degree sufficient to permit separation by gravity, centrifuging, etc.

The solvent should be substantially inert to the plexand and to the compounds of the mixture and also to the urea. Preferably, it should also be heat stable, both alone and in contact with urea, at temperatures at which the desired plexad is not heat stable.

As indicated above, the solvent may be either singleor multiple-component. It is sometimes convenient, partcularly where the plexad is separated by gravity, to utilize a two-component system, as water and an alcohol, glycol, amine or diamine, and preferably a lower aliphatic alcohol such as methanol or ethanol, or a watersoluble aliphatic amine such as piperidine. Such a solvent, partially saturated to super-saturated with urea, lends itself readily to a continuous process for separation by plexation.

Solutions containing sufficient water to minimize the solubility of the hydrocarbon derivatives in the urea solvent, are often employed. The minimum quantity of water required in such instances depends upon the polarity and the molecular weight of the hydrocarbon derivative, or plexand, being treated and, in general, this quantity will be greater with more polar plexands, and with lower molecular weight compounds.

In certain cases the use of single-component solvents is advantageous. Single-component solvents other than alcohols may be employed, although they are normally not as useful as the lower aliphatic alcohols. Glycols may be employed as single solvents, yet ethylene glycol is generally not suitable in gravity separation operations due to the high density of the urea-saturated solvent. The higher glycols and particularly the butylene glycols may be advantageously employed. Diamines such as diamine-ethane, -propane and -butane may likewise be employed. Additional useful solvents include formc acid, acetic acid, formamide, acetonitrile, branched chain hydrocarbons, di-alkyl ethers, esters of carboxylic acids, and alkyl halides; although formic acid, acetic acid and formamide are subject to the same limitation as ethylene glycol.

Solvents generally useful when mixed with sufficient Water, ethylene glycol or ethylene diamine, to render them substantially insoluble in the derivatives being treated, are selected from the class of alcohols such as methanol, ethanol, propanol, etc.; ethers such as ethylene glycol dimethyl ether; and amines such as trimethylamine, hexyamine, piperidine. When gravity separation is employed, the mixed solvent is preferably subject to the restriction that the density after saturation with urea must be less than 1.0-1.1.

() T ypcal separations In order that this invention may be more readily understood, typical separations are described below with reference being made to the drawings attached hereto.

(a) Separation of more highly unsaturated compound from less highly unsaturated c0mp0uud.-The procedure which may be employed in effecting the separation of a more highly unsaturated compound from one less unsaturated, may be essentially the same as that described in copending application Serial No. 4,997, tiled January 28, 1948. The plexand obtained in decomposing the plexad obtained in a urea treatment of a mixture of such compounds is very pure provided that only the less unsaturated compound forms a plexad and provided the plexad be carefully freed of occluded antiplex before it is decomposed. For example, substantially pure oleic acid is separated from the plexad obtained in the treatment of a mixture of the same and linolenic acid, for the latter does not form a plexad.

.Tn Figure 1, a charge comprising a plexand and an antiplex, for example oleic acid and linolenic acid, respectively, enters through line 1, to be contacted with urea solution from line 2, and the charge and solution are intimately mixed in mixer 3. In case the charge undergoing treatment is rather viscous at the temperature of plexad (oleic acid-urea) formation, it is advisable to provide a diluent, such as for example, a naphtha cut which may be recycled within the process, as described later, and joins the charge from line 4. Diluent make up is provided by line 5.

From mixer 3, wherein there is achieved an intimate mixture of urea solution and charge, the mixture flows through line 6, heat exchanger 7, and cooler 8 into settler 9. There may be some or a good portion of plexad (oleic acid-urea) formed in mixer 3, but in general, it is preferred to operate mixer 3 at a temperature somewhat above that conducive to heavy formation of plexad.

I hen in heat exchanger 7, the temperature of the mixture is reduced, and in cooler 8 adjusted, so that the desired plexad is formed. It will be recognized that this showing is diagrammatic, and that the heat exchangers and coolers, heaters, etc., shown will be of any type suitable, as determined by the physical characteristics of the materials being handled.

For the mixture in question, temperatures of operation in the range of 25-50 C. are most suitable. When relatively low molecular weight compounds, for example those containing from 610 carbon atoms per molecule, saturated urea solutions in polar solvents are employed at temperatures from 10 C. to 20 C. When the compounds contain from lG-l6 carbon atom per molecule, saturated urea solutions are also employed, but at temperatures in the range of C.-30 C. It should be noted, however, that many compounds such as the esters of stearic acid form very strong plexads; when treating such compounds, it is desirable to carry out the separation with a urea solution containing from 40-80 per cent of the amount of urea required for saturation.

From cooler 8, the plexad-containing mixture flows into settler 9. This settler is preferably so managed that there is an upper phase of antiplex (linolenic acid), an intermediate phase of urea solution, and a lower region containing a slurry of plexad in the urea solution. The incoming mixture is preferably introduced into the solution phase, so that the antiplex may move upward and plexad downward, through some little distance in the solution, to permit adequate separation of plexad from antiplex and antiplex from plexad.

Antiplex will be removed from settler 9 by line 10 and introduced into fractionator l1, wherein the diluent is removed, pass overhead by vapor line 12 and eventually to use through line 4. Recovered antiplex (linolenic acid) passes from the system through line 13. Obviously if no diluent be used, fractionator 11 will be dispensed with.

Plexad and urea solution, withdrawn from settler 9 through line 14 are passed through heat exchanger 7 and heater 15 to enter settler 16 through line 17. In this operation, the temperature is so adjusted that the plexand (oleic acid) is freed from the plexad and, in settler 16, the plexand rises to the top to be recovered from the system by means of line 18. The urea solution, thus reconstituted to its original condition by return to it of that portion of the urea which passed into plexad, is withdrawn from settler 16 by line 2 and returned to process. Naturally, in a process of this kind there are minor mechanical and entrainment losses of urea solution, etc., and urea s0- lution make up is provided for by line 19.

in many cases, the separation of plexad and solution from antiplex may be conducted with greater facility in a centrifuge operation. Such a setup is shown in Figure 2, wherein only the equivalent of that portion of Figure l centering about settler 9 is reproduced. Again in diagram form, the cooled mixture containing antiplex, plexad and urea solution enters centrifuge 20 through line 6. in many cases, it will be desirable to utilize a carrier liquid in known manner in this operation and that liquid may be introduced by line 21. Antiplex will be carried off through line 10, and plexad, urea solution, and carrier, if present, pass through line 22 to a separation step, which may include washing and may be carried out in a settler, a filter, or another centrifugal operation, which operation is indicated diagrammatically at 23. Carrier liquid, if used, returns through line 24, and urea solution and plexad pass through line 14. (Note: Lines 6, 10 and 14 are the same lines, for the same functions, as in Figure l and are identically numbered.)

(b) Separation of saturated para/jin from @lea-In the case where a straight chain saturated paraffin and a straight chain oleiin present in a mixture each form a plexad, a concentration of the saturated paraffin will be obtained. The sharpness of separation will be greater, the greater the difference in the strength o-f the plexads formed with the two types of pure compounds. ln general, this will be greater, the shorter the carbon chain length of the compounds and the more centrally positioned the double bond of the olefin. more concentrated n-octane can be obtained from a mixture of the same and n-octene-2; whereas, an upgrading of n-octane content is obtained with a mixture of the same and n-octene-l. Also, it is more difiicult to obtain separation between n-dodecane and n-dodecene-Z, than between n-octane and n-octene-Z.

The following serves to illustrate a procedure for obtaining separation between a plexand, n-octane, and av secondary plexand, n-octene-Z. This procedure is similar to a sweating or a solvent sweating procedure used in the rening of slack waxes, as is shown diagrammatically in Figure 3.

In Figure 3, a slurry of solid urea in a saturated urea .v

solvent, which is preferably an aqueous alcoholic solution,

inafter referred to for simplicity as plexand and antiplex,

For example, a`

respectively), which enters through line 33. An immiscible solvent charged through line 34 is alsol preferably ernployed; such as a light eut from a straight run naphtha in case the plexand and antiplex have (l) a relatively high viscosity; (2) an appreciable solubility in the urea solvent; or (3) greater density than .the urea solvent. The amount of excess solid urea employed should be sutiicient so that after the plexation is completed the urea solvent remains substantially saturated with urea.

Internal cooling means may be employed in 32 to further cool the mixture and remove the heat evolvedI during the plexation. The temperature employed in 32 will depend upon the chain length of the plexand and antiplex. If the chain length is such that it is not more than one or two carbon atoms greater than the minimum required to obtain plexation with the pure plexand at 25 C., then temperatures in the range of C. to +20 C. should be employed. If the chain length is from two to six carbon atoms greater than the minimum, temperatures in the range of C.-30 C. should be employed; and if the chain length is greater than six carbon atoms beyond the minimum, temperatures from C.-50 C. are used. It will be apparent, then, that conditions of operation vary considerably, conditions selected being those appropriate for the formation of the desired plexad or plexads.

The slurry of plexad, urea solvent land antiplex is pumped, by means of pump 36, through line and cooler 3'7 wherein it may be further cooled if desired, and into gravity settler 38. In settler 38 the antiplex plus naphtha solvent rises to the top and is withdrawn through line 39 into fractionator 40. The antiplex, predominantly n-octene-2, is removed as bottoms from fractionator 40 through line 41. The naphtha solvent is taken from fractionator 40 through line 42, cooler 43, tank 44 and line to be employed in solvent sweating zone 46, Naphtha solvent may also be recycled to fractionator 40 through line 47, by means of pump 48.

In settler 33, the slurry of plexad in urea solvent is taken oit through line 49, heat exchanger and heater S1 in solvent sweating zone (or mixer) 46. A portion of the clear urea solvent may be removed from the center of 38 and recycled, through line 51 and pump S2, to mixer 32 if desired.

It is to be understood that the gravity settler 38 may be replaced by other separation means such as a centrifuge or rotary lter, etc.

The mixture of solvent and plexad is heated in solvent sweating zone 46 to a temperature sufficient to decompose the major portion of the plexand of the nfoctene-Z, while preserving the major portion of `the plexad of noctane. The temperature employed in zone 46 is related to that employed in mixer 32, and will generally be maintained from 10 C. to 20 C. higher in zone 46 than in mixer 32.

The partially decomposed plexads, urea solvent, and naphtha mixture is passed from zone 46 through line 53 to settler 54. The naphtha containing plexand, n-octanc, and some antiplex, n-octene-2, is recycled through lines S5 and 33 to mixer 32. The slurry of undecomposed plexad is withdrawn from the bottom of settler 54 through line 56, heat exchanger 57, heater 58 into settler 59. The plexad is thus heated hot enough to cause complete decomposition or reversion of the plexads and solution of the urea in the urea solvent. Temperatures of the order of -85 C. are generally suitable.

Plexand, n-octane, contaminated with naphtha which had been occluded on the corresponding plexad (n-octaneurea) is withdrawn through line 60 into fractionator 61. Naphtha is taken oft overhead from fractionator 61 through line 62, cooler 63, tank 64, pump 65 and lines 66 and 55, to mixer 31. A portion of the naphtha may also be recycled to fractionator 61 through line 67. Plexand, n-octane, is recovered as bottoms through line 68.

Urea solution is recycled from the bottom of settler 59 14 through line 69, pump V70, heat exchangers 57 and 50, and line 51.

Plexand of any desired purity may be obtained by either: (l) increasing the fraction .of the total plexad decomposed in the solvent sweating zone (46), or (2) including a multiplicity of alternating solvent sweating zones and settling zones (54) operating in series.

VII. ILLUSTRATIVE EXAMPLES The following examples serve to illustrate, and not in any sense limit, the present invention.

(a) Separation of 110ctene-1 and n-0cten.e-2.-A mixture 20 parts by volume, comprising 50 volume percent each of n-octene-l and n-octene-2, was agitated at 25 C. with 150 parts by volume of a saturated aqueous urea solution. The resulting mixture was allowed to stand for about 16 hours and then filtered. The recovered plexad was decomposed by contact with water. The hydrocarbon recovered from the plexad comprised 13.5 parts by volume and was richer in n-octene-l than the original mixture, namely 69 volume percent of n-octene-l.

(b) Separation of n-octane from n-octene-L-Six parts by volume of a 50-50 volume percent mixture of n-octane and n-octene-l, was agitated for 15 minutes at 25 C. with 30 parts by volume of a 67 percent aqueous methanol saturated with urea and containing three parts by weight of excess solid urea. The resulting mixture was centrifuged, the upper layer poured ott, and the hydrocarbon recovered from the plexad by decomposition with water. The recovered hydrocarbon, 1.5 parts by volume, contained 55 percent of n-octane.

(1c) Separation of n-octane from n0ctene-2.-The example shown above in (b) was repeated with a mixture containing 50-50 volume percent of n-octane and noctene-2. Here, the hydrocarbon recovered from the plexad, 1.5 parts by volume, contained 61 percent of noctane.

(d) Separation of n-butyl ,stearate from n-butyl oleate.-A solution of 4 parts by volume of n-butyl stearate and 4 parts (volume) of n-butyl oleate in 92 parts (volume) of isooctane, was agitated at 50 C. for 30 minutes with 25 parts (volume) of an aqueous methanol solution saturated with urea at 65 C. The resulting plexad layer was separated from the mixture, and decomposed by contacting the same with water. The ester recovered from the plexad contained 2 parts (volume) of butyl stearate and 0.3 part (volume) of butyl oleate.

The same ester solution was stirred at 50 C. for 150 minutes with parts by volume of the same urea S0111- tion. In this instance, the recovered ester contained 3.75 parts (volume) of butyl stearate and 1.4 parts (volume) of butyl oleate. The antiplex contained 0.25 part of butyl stearate and 2.6 parts of butyl oleate.

The equilibrium concentrations of butyl stearate and of butyl oleate are shown by the following. Butyl stearate in isooctane solvent on repeated treatment with a sat-urated solution of urea in methanol, can be removed to a concentration below 0.1 percent by volume at 25 C. and to a concentration of 0.6 percent at 50 C. In contrast, butyl oleate can be reduced in concentration to 0.8 percent (volume) at 25 C. and 4.1 percent at 50 C.

(e) Separation of dii-n-hexyl) succinate from dnhexyl) maleate.-The separation of saturated from unsaturated compounds is further illustrated by the experimental observation that the equilibrium concentration in the urea plexation of dit-n-hexyl) succinate is below 0.1 per-cent (volume) at 25 C., and only 3.5 percent (volume) at 25 C. for ditn-hexyl) maleate.

VIII. UTILITY From the foregoing description, it will be apparent that the invention has considerable application in the chemical and petroleum arts. For example, hydrocarbon mixtures containing straight chain paraftins, olefins and polyoleiins can be separated into straight chain parailins, straight chain olens and straight chain polyoleflns, respectively.

Also, the invention is useful in eifecting the separation of fatty acids (and their esters) of different degrees of unsaturation, such as those derived from various vegetable oils. This is particularly advantageous in providing concentrated drying oils or acids, relatively free of the nondrying oils and acids for the coating and resin industries. Thus, a mixture of stearic, oleic, linoleic and linolenic acids, or their esters with monohydric or dihydric alcohols, can be separated into their individual components, or into fractions relatively rich in the saturated components, and those rich in the more unsaturated components.

Another application is in making possible the separation of various long-chain saturated amines or amides from the related unsaturated amines or amides. This is illustrated by the separation of n-octadecylamine from mixtures containing the same and n-octadecenylamine.

Still another application of the invention is in conjunction with the process described in related application Serial No. 115,512, tiled September 13, 1949, now abandoned, wherein thiourea is shown as a plexor with highly-branched chain paratlins and highly-branched chain olens as plexands. For example, with a mixture of straight chain parains, highly-branched chain parafns and oletins, it is possible to rst treat the mixture with thiourea to remove the highly-branched chain paraffins in the form of their thiourea plexads and thereafter treat the remaining hydrocarbons with urea to elfect separation of the straight chain parans and olelins. It will be understood that the same mixture can be plexated lirst with urea and then with thiourea.

Halogen compounds can be plexated from mixtures containing the same and form urea plexads, as described above and as described and claimed in application Serial No. 115,511, now abandoned in favor of application Serial No. 374,707, led August 17, 1953. Compounds characterized by a nitrogen-containing substituent are also plexated from mixtures containing the same and form plexads with urea, as described above; this subject matter is also described and is claimed in application Serial No. 115,515, Patent No. 2,681,332. Sulfur-containing compounds are also plexated from their mixtures, and form plexads with urea, as described above and as descrbied and claimed in application Serial No. 255,943, led November 13, 1951, Patent No. 2,681,336, as a continuation of application Serial No. 115,516, which has been abandoned. Plexation of compounds containing cyclic substituents, and urea plexads thereof, are described and are claimed in application Serial No. 116,- 593, Patent No. 2,681,334. Plexation with urea of various terminally substituted compounds from mixtures containing the same and non-terminally substituted cornpounds, described above, is also described and is claimed in application Serial No. 115,517, Patent No. 2,681,333.

Urea plexation of a non-terminally mono-substituted compound from mixtures containing the same and a nonterminally poly-substituted compound is described and is claimed in application Serial No. 115,513, now U. S.

Letters Patent 2,642,422. Urea plexation of mixtures containing aliphatic compounds of dierent degrees of unsaturation is described and is claimed in application Serial No. 115,514, now abandoned. Urea plexads of aliphatic hydrocarbons of different degrees of unsaturation are described and are claimed in application Serial No. 115,518 (now U. S. Letters Patent 2,642,423), of which this application is a division.

Said applications Serial Nos. 115,511; 115,513 through 115,518 and 116,593 were led concurrently with parent application Serial No. 115,518 on September 13, 1949.

I claim: l

l. The method for separating a straight chain alpha mono-olen (I) having at least about eight carbon atoms in the chain, from a mixture containing the same and a straight chain mono-olefin (II) having at least about eight carbon atoms in the chain and having the double bond more centrally positioned in the chain than the double bond of (I), which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said mono-olefin (1); and separating said complex from the resulting reaction mixture.

2. The method for separating a straight chain alpha olefin (I) having at least about eight carbon atoms in the chain and having no more than one additional non-terminal olefin group per molecule, from a mixture containing the same and a straight chain olen (Il) having the sarne number of carbon atoms in the chain as (l), being free of a double bond at a terminal carbon atom and having less than three double bonds per molecule, which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said olen (1); and separating said complex from the resulting reaction mixture.

3. The method for concentrating n-octene-l from a mixture of n-octene-l and n-octene-Z, which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said n-octene-l; separating said complex from the resulting reaction mixture; decomposing said complex to set free said n-octene-l in more concentrated form than in said first-mentioned mixture.

References Cited in the tile of this patent UNITED STATES PATENTS 2,499,820 Fetterly Mar. 7, 1950 2,518,677 Garner et al. Aug. 15, 1950 2,520,715 Fetterly Aug. 29, 1950 2,520,716 Fetterly Aug. 29, 1950 2,557,257 Melrose June 19, 1951 2,596,344 Newey et al. May 13, 1952 OTHER REFERENCES Bengen et al.: Experientia, vol. 5, part 5, page 200, May 15, 1949. 

1. THE METHOD FOR SEPARATING A STRAIGHT CHAIN ALPHA MONO-OLEFIN (I) HAVING AT LEAST ABOUT EIGHT CARBON ATOMS IN THE CHAIN, FROM A MIXTURE CONTAINING THE SAME AND A STRAIGHT CHAIN MONO-OLEFIN (11) HAVING AT LEAST ABOUT EIGHT CARBON ATOMS IN THE CHAIN AND HAVING THE DOUBLE BOND MORE CENTRALLY POSITIONED IN THE CHAIN THAN THE DOUBLE BOND OF (1), WHICH COMPRISES: CONTACTING SAID MIXTURE WITH UREA UNDER CONDITIONS APPROPRIATE FOR THE FORMATION OF A CRYSTALLINE COMPLEX OF UREA AND SAID MONO-OLEFIN (1); AND SEPARATING SAID COMPLEX FROM THE RESULTING REACTION MIXTURE. 